Method and apparatus for advancing subterranean pipe



L. RANNEY Feb. 23, 1954 3 Sheets-Sheet 1 Filed May 27, 1949 l gi w \mimm NH J a mmmmmmmmm '@@h F fifim m :W mm an 6 m. m

WmW N INVEA/raz LEO RHNNEy' HTTORNEX IPE L. RANNEY Feb. 23, 1954 7 METHOD AND APPARATUS FOR ADVANCING SUBTERRANEAN P Filed May 27,

3 Sheets-Sheet 2 INVENTOR, LE0 ,Rmwvzy -87 M L. RANNEY Feb. 23, 1954 METHOD AND APPARATUS FOR ADVANCING SUBTERRANEAN PIPE 3 Sheets-Sheet 3 Filed May 27, 1949 INVENTOR.

A TTO RNEy.

Patented Feb. 23, 1954 METHOD AND APPARATUS FOR :S'UBT'ERRANEAN PIP Leo Ranney, Morro Ba ADVANCING E y, Califi, assignor to Ground Water Inc., a corporation of New York Application May 27, 1949, Serial No. 95,653

2 Claims.

This invention relates to methods and devices for the driving of underground pipes.

In my Patents Nos. 2,126,575 and 2,126,576 I have described a method. of introducing subterranean pipes particularly for the construction of water collection systems in aquifers.

In such operations pipe is forced into .the earth in .an initially generally horizontal direction. The pipe is perforate and has a digging head at its forward end. The digging .head is hollow and is provided with a port. An internal imperforate pipe is positioned inside the perforate pipe and is connected to the digging head. The rear end of the perforate pipe, i. e., the end remote from the digging .head, is closed, as .by

a suitable packer through which the internal pipe passes. The internal pipe may. discharge into any suitable fluid collecting system. The exterior of the perforate pipe may also be packed off against the earth at the point .of entry into the earth.

In such operations, especially when the formation into which the vpipe is driven contains fluid, such as water, under pressure, the fluid enters through the perforations into the outer pipe .and through the digging head nozzle and into the internal pipe. .Since the ,rear end of the external pipe is closed by the external packer, the flow is through the digging head and through the internal pipe. In this manner a mixture of loose sand and fluid, i. e., water, is withdrawn from the formation ahead of the digging head'.

The removal of the sand in the stream of fluid entering from the formation into the inner pipe is selective, that is, the ifiner grains are suspended in the fluid and pass therewith, While the larger grains or the more consolidated material remains in place. The net result is an increase in porosity and permeability in the formation surrounding the advancing tube.

In such a procedure the direction of progress of the pipe through the formation may, in certain circumstances, be an important problem.

The deviation of the pipe from a predetermined line is influencedby several factors. Thus, gravity tends to induce the pipe to plunge downward in the direction of the pull of gravity. Of course, variations in the formation, such as the direction of dip, will tend to cause the p pe to deviate from a horizontal line, or variations in the nature of the formation, .or the existence of boulders will cause the pipe to deflect.

However, .I have found that one ofthe most important considerations 'is the Withdrawal of sand which .causes a weakening of the formation in the direction of maximum withdrawal and therefore has a directional effect.

I have devised a means for employing the above principle of action to control the direction of movement of the pipe.

Summarizing my invention, I provide :a pipe system which may be advanced non-rotatively into the formation in a desired direction and selectively remove portions of the earth in the (H rection of desired .advance, and in a preferred embodiment I provide at the forward end a dig= ging head having a port for passage of san and fluid from the formation into the digging head and for flow throughthe pipe system. I also provide means for positioning the port at a "selected position around the axis of said digging head in a predetermined geographical relation to the horizontal, whereby the digging 'he'ad will deviate in an axial direction in a predetermined manner. v V A v In my preferred embodiment I seal the exterior of the pipe in such manner that the formation fluid is forced to passthrough the selectively positioned port in the digging head and through the pipe and is prevented from passing around the pipe.

These and other ob'ie'cts of my invention will be further described in the following specific-ti tion taken together with the drawings, which Fig. i is a fragmentary plan view of mystructure for driving subterranean pipes:

Fig. 2 is a fragmentary section taken on line 2- 2 of 1; V

Fig. '3 is a section taken on line 3-3 of Fig. 4 is a fra mentary Section taken on line '4-4 Fig. 1;

Fig. 5 is an exploded perspective view of the head of the valve element;

Fig. is a section taken on line G 6 of Fig. 4;

Fig. 7 is a partly sectional view illustrat ng a method and device for sealing the ends ef the pipe system to prevent flow of fluid fromthe formation while adding pipe; and I,

Fig. 'iS another Stag-8 Of the same plddll f.

As described in said aforirientiofidpat V a structure is provided in the earth at a level at which the pipe is to enter into the earth. structure may be cemented at the race of the earth formation into which the pipe to be driven and may be provided with orts T61 the passage of pipe" through the cement wall. .8 convenient and c nventional method for providing such structureisto sink a concrete caisson to the point in the earth at which the pipe to be jacked. The cylindrical wall of the caisson at the point where the pipe is to enter the formation is provided with a port. Such a wall is illustrated at I (Fig. l) with port indicated at 4. At this level is provided a supporting structure for a pair of jack cylinders 2 provided with a piston rod 3 carrying a yoke 5 which abuts the pipe 6 which is to be pushed into the formation.

The pipe 6 is usually slotted with slots 1 throughout its length. A packing member is first provided at the port, as is illustrated more clearly in Fig. 2. The packer is in the form of a hollow truncated cone 3 having an annular flange Hi. It may be made of rubber or of any suitable elastomer. It is introduced through the port A with the flange H3 against the face of the caisson and is clamped against the face of the caisson by a suitably shaped ring H which is held against the face of the flange by means of bolts l2 to seal the flange l against the face of the caisson. The pipe 6 and the digging head is passed through the packer, as is shown in Fig. 2.

The forward or digging end of the pipe is threaded at l3 and a ho low digging head M is screwed onto the pipe. The digging head M has an internal curved shoulder l and an outer conical section It terminating in a digging point H. The digging portion is provided with ports I8a, I81), I80, and I811, as shown, disposed 90 apart around the axis of the digging head. A removable plug I9 is screwed into the interior of the digging head at its cylindrical portion. At the forward end of the digging head and concentric with the axis of the digging head is a pilot bore 29'. The entrance end of the plug at 2| is curved at 20 to the same curvature as the curved shoulder IS. The plug has an internal bore 2| coaxial with the axis of the digging head.

The forward end of the plug i3 has a conical portion 22. A hollow valve member is formed with a conical section 23 and a rear conical portion 24 having a central bore 28 and a depending lip 29. The conical portion 22 is parallel to the interior cone 24 of the digging head valve. The conical section 23 is para lel to the conical section 25. The forward end of the valve has a rod 25 which fits into the pilot bore 23 positioned axially of the digging head. The conical portion 23 carries a port 30 which is adapted to register with each of the ports Illa, I81), |8c, and Md. The port 30 bears a known axial relationship to the lip 29, as, for example. illustrated, 180 apart. The surfaces 22, 24 and 25 and 23 need not be conical but may be any similar surfaces of gyration such that the interna cone of the hollow valve member may be rotated over the complementing inner surfaces of the digging head. i. e., are in rotative sliding relationship.

The internal imperforate pipe 32 carries a slot 3|. It passes through the bore 2| and the lip 23 enters the slot 3|. At the rear ends of the pipes 6 and 32 packers are provided to seal the space between the exterior of the imperforate pipe 32 and the interior of the perforate pipe 6. These packers are composed of a series of rings 33 having internal flanges 34. Between the rings are packing elements 35 composed of annuli. having ring flanges 36 and 31. The external diameter of the flange 36 is somewhat larger than the internal diameter of the pipe 5 and that of the internal diameter of the flange 31 is somewhat larger than the external diameter of the pipe 32. It will be seen that there is such a packer between each ring. The packers may be made of rubber or any other packing material of sufficient flexibility so that the flanges 36 and 3'! may be pressed against the interior wall of the pipe 6 and the exterior wall of the pipe 32 when the pipe 32 is in position. In order to hold the packers in position against the fluid pressure of the formation, keys 39' are inserted into the slots '1 in that portion of the slotted pipe 6 inside the caisson L It will thus be seen that when the digging head is disconnected from the pipe 5 and from the pipe 32 and with the plug l9 unscrewed from inside the digging head, the hollow valve member may be pushed inside the digging head with the rod 26 entering the pilot bore 29 and the surface 23 abutting and sliding over the interior conical surface of 25. The plug l9 may be screwed into position with the cone 24 abutting the conical section 22 of the valve. The digging head may then be screwed onto the slotted pipe 6. The packers may then be introduced into the rear end of the pipe section.

Having introduced the packers and the flanges and the rings into the interior of the pipe, the imperforate pipe 32 carrying valves 38 and 39 on its rear end is introduced and is guided by the curvature of the internal shoulders l5 and the curved portion 20 to enter into the bore 2|. The pipe 32 is then rotated until the slot 3| in the pipe coincides with the lip 23 whereupon the slot 3| passes over the lip 29 and the pipe 32 enters the bore 28.

Pipe 32 may be marked with a mark in line with the slot 3| so that when the pipe is introduced into the lip 24 the relative axial relationship of the lip and therefore the port 33 with the mark at the end of the pipe is known. The pipe 32 may then be rotated. This rotates the valve so that the port 30 is in register with one of the ports |3a to I811, inclusive, whichever one is selected. It will be seen that therefore all of the other ports are blocked and the interior of pipe 32 communicates with the selected port.

The pipe section is then introduced through the packer 9 and abutted against the yoke 5 with the valves 38 and 33 at the end of the pipe 32 I open and connected to line 43 for disposal of the fluid. The jack pushes the pipe 6 through the port into the formation. If desired, removable slips 5' may be placed between pipe 32 and the yoke 5 to cause the yoke to advance the pipe 32 simultaneously with pipe 6. Usually, however, the sag of the pipe 32 inside the pipe 6 is suflicient to give a rubbing contact which drags the pipe 32 along with pipe 6 without the use of such slips. When the full stroke of the jack has been extended to push the section of pipe into the formation, the jack is retracted.

During this procedure, assuming that the pipe has entered a formation containing fluid under pressure, as, for instance, in an aquifer, or an oil zone, fluid under pressure enters from the formation into the slots 1 and exerts a pressure against the packer elements 35, causing them to move down the pipe. However, this is prevented by the retaining key 39' which is introduced through the slot and abutted against the packer elements. The keys are used in dulicate and may be removed one at a time and shifted in position to hold the packer inside wall at the end of each section of pipe as it passes through the packer 9. It will thus be seen that the pipe 32 is sealed inside the pipe 6 so that fluid may not be by-passed through the pipe 6 and around the pipe 32 to the interior of the caisson. The pressure of the fluid in the formation also enters into the annular p ce between the interior of the packer 9 and the wan or the port I, compressing the packer around the :pipe 6, sea-ling the pipe -6 into the ports so no fluid can =enter *on the exterior of the pipes into'the caisson.

The fluid under pressure is thus caused to pass through the selected ports 18a to 812 through the port -31 into the interior of the pipe St-and discharge from the end of the pipe 32 under the controlof the valves-"38 and 3 9.

The iiuid passes throug'hpipe 32, by the valves '33 and 3-9 and through the T box -89, closed by plug i l in the orifice 32 through the disharge conduit 13 to storage or other disposal. When the section of slotted pipe and internal pipe 32 have been advanced to the face of the -=caisson, it

becomes necessary to add additional slotted pipe and imperfoeate pipe. While in *the case of the production of water the addition 'of the perforate and imper'forat-e pipe may be accomplished as in the case of the procedures described 'in't'he above mentioned patents, the following procedures may be employed when it is desired to prevent the escape of -formation fluid during addition or pipe sections.

When the pipe '6 has been formation through the is adjacent the wall l advanced "into-the 'port 4 the'end of the pipe and the-packer is at the end of'the pipe held in place 'by the'keys 39. The pipe 32 and the valves Stand 39 and the plug '42 and pipe 43 are inside the caisson, with both valvesti) and BS-closed, as shown in Fig. 7. The

jack yoke is removed from the jack after retraction.

The plug a: is removed and the plug packer 44 positioned on the end of a long rod to inserted through the orifice 42,- valve 39 is opened and the packer is pushed through the valve. lhe paoker is long enough to span the valve so that it closes ed the pipette it passes through the valve. Valve '38 is opened and the packer is shoved into position beyond the valve flange and into the pipe '32, as shown in Fig. 8. The plug M may beadvanced by means of a jack -58 and steadied "by one "or more split bearing bushings '41 suitably and reinovably positioned the caisson i The flanges '43 are split, the bearings '41 separated and removed from the rod, and the conneotion i'3 separated at the-flanges 49 and-the'assembly of valves slid backward along the rod. with the jacks 46 removed, the end of the rod. If the pressure in the tube 3-2 is high, a suitable gripping means, such as stacks With suitable removable slips "such as 5', but of propersize to grip the rod 45, is inserted between the end of the tube 32 and the valve 38, after it assembly is slid off the has been slid back suiiicient-ly, to hold the rod 45 7 against movement when the jacket iswithdraw-n.

A second joint of pipe 32 with a flange M at the inner end thereof is then slid over theend of the rod 45, it being held suitabl to permit the passage of the pipe over the end "of the "rod 45.

'Thus the holding means 5, placed adjacent the end of the pipe 32 near-the plug -45, will hold the rod ie against movement and permit the new section of pipe to be the jack 46 can be placed against theend-of the rod 45 and the holding means removed by removal of slips =5". The pipe sections are then joined, as by screwing the-pipes together, and the pipe 32 extended. The intermediate holding means is then placed to engage the rod 45 at the end of the newly added section of pipe 32; The holding jack to .iatthe lifiihai lfidfi than removed-anda section nfhine 6:;passed-over the end of the. rod it. comes-up. tojtheinten slid over the end of #5 savages mediate rod support 5, with 'the'end of :the irod145 projecting *beyond the end or the :new section of pipe 6. 'ho'ldin'g jack #6 is then placed at the end of the rod 45. The intermediate rod support is removed 'by-remova l "Ofilhfi yoke of the jacks or toy the removal of the slips 5 :and'the backing plate between "the end of 6 and the yoke. The plate-maybe split ior this purpose and the new section pipe 6 advanced until it abuts the pipe as projecting from the port '4. The pipes are joined as b welding or by means of a screw joint. The i-n termediate holding means '5 is then placed on the rod 45, the holding jack is removed, and the valve assemhiy slid over the rod 45 with the end of the rod #5 projecting beyond the port $2. The holding jaek 4E placed at the end of the rod 55 and the intermediate rod holding means :5 is withdrawn, and the ifianges 48 011 the valve 38 and on the inner-end of pipe 3-2 are joined, and the plug 4'4 then withdrawn between the valves '39 and 38. Valve 38"is closed and the plug 'withdraem eenip'ietely. Valve 39 is closed or left open and the plug 51 placed in position and the jack yoke 5 placed in position loy replacement of the yoke '5 if originally removed or by the rep'i'a'cement of slips 5' and the hacking plate between the end or thenew section of tend the yoke 5, they only had been removed.

Assuming, for the'purpose of illustration, that the port 180 is the one in register "with the port 3-0, as illustrated in Fig. 6, ."there will he a selective withdrawal of-sand underneath the digging head 4 and underneath the port 1l18c,:and this will weaken the formation underneath the digging heaQcaUsingt-he digging head to plunge in the direction of the port 180. If, now, it is desiredto change the direction of the deviation of the here hole, for example; suppose it is desired to deviate the pipe to the right, the pipe 32 inside the caisson :is rotated 90 in a counterclockwise direction. This brings port 3| into registry with port [81). The formation will therefore be selectively withdrawn from the side of the digging head adjacent the port 1% and the'formation will thus be weakened at that p01- tion and the digging head will deviate to the right. It is preferable to make this rotation of 3 2 with the packer 14 in position and the valve system 38, 39 removed as described above.

If it is desired to deviate the digging head to the l'eity the pipe 321s rotated through the angle necessary to movethe port '30 into registry with the port Md and the selective withdrawal of formation through the port 30 and into the pipe 32 will cause the digging head to deviate to the left. In like manner, it it'is. desired to deviate the digging head in an upward direction, the pipe 32 is rotated to "bring the port 3'9 into registry port E82: aind a selective withdrawal of the formation irom above the digging head will cause theiheard "to "deviate in an upward direction as the pressure. is exerted .by the-jacks to move the pipe intothe formation. I

Since til-reposition of the :slot 13f its always known because of the mark positioned upon the pipe 32iat the inside :of the caisson, which is alwaysin line with theslo't 3.1;, the position, of theslot 31 may beat all times determined from the position of thatimairkon the pipe 32 on the interior or the caisson. Additionally, since the initial position of the open port as the pipe 5621mm igronndrisknown .hy rotation-of them? the portsgare to stop the of :ztor-mation and opened to start the flow, the number of stoppages-and nesump undesirable because of safety-reasons or for &70389 tion of flow as the pipe is rotated is a further check on the position of the open port.

I have described the above apparatus and process in which the direction of advance is in a generally horizontal direction. However, as will be recognized by those skilled in the art, the same principle may be applied when the pipe is introduced to travel in either a vertical direction or in any direction deviated from thehorizontal or vertical and in any desired azimuthal direction. The opening of the selected port causes the pipe to deviate in the direction of the open port which thus has a predetermined position with respect of a vertical and a horizontal geographic plane, i. e., in a predetermined azimuthal direction and in a predetermined vertical and horizontal deviation, both in respect of the geographic vertical and the geographic horizontal direction, and also, of course, in respect of the axis of the boring head and pipe 6. Thus, by positioning the open port at such predetermined position, I may non-rotatively advance the pipe in a predetermined deviated direction from the vertical or horizontal plane and in a predetermined azimuthal direction.

It will, of course, be understood by those skilled in this art'that if the initial direction of entrance through port 4 is not horizontal, the cement face of the formation and the port l, as well as the jacks 5, may be faced in the initial direction whether it be vertical, horizontal, or at any degree of inclination or in any geographic direction desired.

The apparatus described above, inthat it provides means for selectively positioning the port in the digging head at predetermined positions around the axis of the digging head, makes possible directional non-rotative advance of pipes underground where there is insuflicient formation fluid or no formation fluid to cause the removal of material from the earth in the manner described above. I

In such case I create or augment the fluid pressure in the formation by introducing fluid under pressure from an extraneous source through pipe 32 discharging the fluid inthe formation through the selectively opened port, as described above. Pumping is continued. As fluid is pumped into the formation the fluid migrates out from the digging head, andthe pressure and volume of the formation fluid is increased. In this manner fluid at considerable pressure accumulates in the formation in the region of the digging head at the pressure created by the pumping operation. When the desired been reached, the pump may be by-passed and the pipe 32 connected to a fluid receiving sump, for example, the pipe 32 is vented to atmospheric. The fluid in the formation under the stored pressure vents through the formation and the open port and into the pipe 32 carrying with it material from the formation in the same manner and to the same effect as in the case of the flow of natural formation fluid 'described above.

The fluid employed in such case may be the same as is present in the formation where the purpose of this procedure is to augment the natural flow. But it need not be the same and may be any fluid such as water, oil, solvent material or a gaseous fluid such as air, carbon dioxide, natural or illuminating gas where the use of such material is not' undesirable 'as'a contaminant or other pump pressure has practical reasons.

Where a-gas is used either to augment the fluid in the formation or to add pressure to the fluid in the formation, the gas may be used alone or in mixture with other solutions in the fluid. Thus, when using water, I may also employ CO2, the CO2 dissolving in the water at the high pressure employed. As a further example, when using petroleum oil as the liquid, I may employ natural gas and form a solution or foam of the gas and oil under the pump pressure. Upon the release of pressure the expanding gas acts to impart kinetic energy to the fluid. The flow of the oil and water in the formation is thus augmented as in the case of naturally occurring oil field reservoirs.

The artificially induced or augmented flow of fluid, liquid, or gas, or jointly liquid and gas, carries with it material from the formation through the open port and into the pipe 32 with the effect previously described.

The steps of pressurizing and releasing may be repeated in cycles at sufficient frequency and for a sufiicient number of times to remove the desired amount of material in order to permit the progress of the digging head and pipe system in the desired manner as described above. When the permeability of the formation is so low, i. e., the formation is so tight, that the employment of the above method of augmentation of formation fluid pressure or volume is impractical or when for any other reason it is not desired to follow the above procedure in more permeable, but still relatively tight, formations, I may employ the following procedure.

I pump the fluid, gas, liquid, or gas and liquid through pipe 32 and raise the fluid pressure in the formation to any desired magnitude that my pumping system may permit. I may thus, particularly if the weight of the over-burden is not too excessive, lift the formation and create cavities and fissures in the formation around the digging head. These cavities are thus fllled with fluid under the pump pressure often approximately equal to the weight of the over-burden. When the pressure in the pipe 32 is vented, as described above, the fluid enters at high velocity, aided by the squeezing effect on the fluid of the lifted over-burden, carrying material from the formation in a manner similar to that described above.

In the above technique I may control the reentry point of the fluid from the formation into the pipe 32 by positioning the port 36 of the valve member 23 over the selected ports 13a to ltd. In this respect the action of the formation fluid under the artificially created formation fluid pressure is similar to the naturally occurring formation fluid in the process described above.

Because I am able to position the open port at any desired position axially about said pipe, as described above, and to in effect rotate said ports about said digging head by opening and closing the ports l8q, to hid in sequence, by rotation of the pipe 32 and the valve 23, I can also employ my structure to cause a jet cutting or erosion action to occur about the digging head and thus non-rotatively advance the pipe system and remove detritus or material from the formation in the manner described above.

Thus when the earth material through which the digging head is to pass imposes a large resistance togthe advance of the digging head, fluid may be'puz'nped into and through the pipe -32 to discharge through one of theports. By rotating the valve member 23, the earth material may be worn away on all sides of the digging head or selected regions by selectively opening the ports in the chosen region. I can thus create a cavity located at the desired geographic position with respect to the axis of the digging head and cause the advance of the digging head and pipe into such cavity and in a desired direction.

33y rotating the pipe 32 and non-rotatively advancing the pipe 6, ports [8a to IM act as a circumferential spiral jet to cut a circumferential spiral kerf which may be of the desired diameter and so permit the advance of the pipe into the cavity with reduced resistance.

Where the formation is unconsolidated as, for example, where the formation is a mixture of gravel and sand and is too permeable to permit of the creation of a body of fluid in the formation adjacent the digging head under a desirably high artificially created fluid pressure, I inay pump liquid through any of the selected portsand wash the sand away from the digging head in the vicinity or direction of the open port. The fluid transports the sand to more remote regions of the formation to pack the formation more firmly in such more remote regions but weakens the formation in the direction and region of the open port. Thus, the digging head advances in the weakened direction to advance in the desired direction. For example, if port I80 is open, the fluid exiting from I80 will flow downward and then the flow pattern is around the digging head and in a generally upward direction. This washes sand out from under neath the digging head, i. e.,. in the direction of the port I80 and deposits the sand in the gravel in the direction of la, [8b, and "id. The earth is weakened in the direction of I80 and strengthened in the direction of ma, I8b, and HM. The earth is not only more consolidated in the regions where the added sand is deposited, but the reduction in the bulk density of the earth in the direction where the sand is removed and its increase in the direction where it is deposited results in the diminution of skin friction v in the regions of the lesser density and increase in the regions of greater density. This deflects 10 the digging head in the direction of the port I80. While I have described a particular embodiment of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may bemade Within the spirit of the invention as set forth in the appended claims.

I claim:

1. An apparatus for forcing pipe under-ground, comprising a pipe, a hollow digging head at one end of said pipe, a plurality of ports spaced around the axis of said head and pipe, selective opening and closing means for said ports, means operable from the other end of said pipe for actuating said selective opening means to open selectively one only of said ports, means for forcing said pipe into the earth, and means for withdrawing fluid from the formation through an open port and through said pipe.

2. An apparatus for forcing pipe under ground, comprising a. hollow digging head at one end of said pipe, a plurality of ports spaced around the axis of said pipe, means for selectively closing all but one of said ports, said means including a closure means for all but one of said ports, and including also means operable from the other end of said pipe for actuating said closure means to selectively close all but one of said ports, and to selectively establish fluid communication between the outside and inside of said hollow digging head through said selected open port, and means for conducting fluid passing through the said open port to a remote location.

LEO RANNEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 405,200 Chapman June 11, 1889 1,994,884 Chew Mar. 19, 1935 2,121,858 Chew June 28, 1938 2,126,575 Ranney Aug. 9, 1938 2,126,576 Ranney Aug. 9, 1938 2,198,386 Hiester et al Apr. 23, 1940 2,212,491 Appleby Aug. 27, 1940 2,492,151 Holm et a1 Dec. 27, 1949 

